In-plane and out-of-plane correlations of light charged particles and neutrons emitted in the Cl-35 (260 MeV)+Mg-24 complete fusion reaction have been measured to investigate deformation and angular momentum effects upon the decay of Cu-59 compound nucleus. An array of 21 BaF2 crystals has been used to identify the light charged particles (Zless than or equal to4) and neutrons emitted in coincidence with heavy fragments (Zgreater than or equal to5) detected in six ionization chamber telescopes. Coincident energy spectra and angular distributions of neutrons, protons, and alpha-particles have been described by the statistical-model calculations with nuclear level densities tuned to take account of deformation effects in the emitters. This spin-dependent approach suggests the onset of large nuclear deformation in Cu-59 at high spin. This conclusion is consistent with the recent observation of a superdeformed band in the Cu-59 nucleus.

The peripheral and semiperipheral reactions in ${}^{35}\mathrm{Cl}{+}^{197}\mathrm{Au}$ have been studied at 30 and 43 MeV/nucleon. The nonequilibrium $\ensuremath{\alpha}$ and IMF components have been observed in the experiment. The fraction of nonequilibrium emission decreases with an increase in the atomic number of the projectilelike fragments but, for a given projectilelike fragment, it increases with the charge of the emitted particles. The characteristics of quasiprojectiles reconstructed from their decay products reveal several features reminiscent of damped reactions at lower bombarding energies. The atomic number and deflection angle of projectilelike fragments depend strongly on their kinetic energy or dissipated energy. At 30 MeV/nucleon, the experimental data can be explained by a deep inelastic transfer model. One-body dissipation is still the main mechanism for the energy and angular momentum dissipation. However, at 43 MeV/nucleon, deep inelastic transfer models can predict only the experimental tendency. Two-body dissipation plays a more important role at higher incident energies. The similarity observed in the decay product distributions, as a function of excitation energy, suggests that the excited quasiprojectiles formed in binary collisions might approach thermal equilibrium for both incident energies. The decay products have been analyzed with sequential-binary and simultaneous-disassembly statistical decay models. Both statistical models are able to provide good agreement with the experimental observables except for the mean kinetic energy of the products.

Compound-nucleus fusion and binary-reaction mechanisms have been investigated for the Cl-35+Mg-24 system at an incident beam energy of E-lab=282 MeV. Charge distributions, inclusive energy spectra. and angular distributions have been obtained for the evaporation residues and the binary fragments. Angle-integrated cross sections have been determined for evaporation residues from both the complete and incomplete fusion mechanisms. Energy spectra for binary fragment channels near the entrance-channel mass partition are characterized by an inelastic contribution that is in addition to a fully energy damped component. The fully damped component which is observed in all the binary mass channels can be associated with decay times that are comparable to, or longer than, the rotation period. The observed mass-dependent cross sections for the fully damped component are well reproduced by the fission transition-state model, suggesting a fusion followed by fission origin. The present data cannot, however, rule out the possibility that a long-lived orbiting mechanism accounts for part or all of this yield.

Compound-nucleus fusion and binary-reaction mechanisms have been investigated for the ${}^{35}$Cl+${}^{24}$Mg system at an incident beam energy of E${}_{\mathrm{lab}}$= 282 MeV. Charge distributions, inclusive energy spectra, and angular distributions have been obtained for the evaporation residues and the binary fragments. Angle-integrated cross sections have been determined for evaporation residues from both the complete and incomplete fusion mechanisms. Energy spectra for binary fragment channels near the entrance-channel mass partition are characterized by an inelastic contribution that is in addition to a fully energy damped component. The fully damped component which is observed in all the binary mass channels can be associated with decay times that are comparable to, or longer than, the rotation period. The observed mass-dependent cross sections for the fully damped component are well reproduced by the fission transition-state model, suggesting a fusion followed by fission origin. The present data cannot, however, rule out the possibility that a long-lived orbiting mechanism accounts for part or all of this yield.

Fusion-fission and fully energy-damped binary processes of the 35Cl+24Mg reaction were investigated using particle-particle coincidence techniques at a 35Cl bombarding energy of Elab≈ 8 MeV/nucleon. Inclusive data were also taken in order to determine the partial wave distribution of the fusion process. The fragment-fragment correlation data show that the majority of events arises from a binary-decay process with a relatively large multiplicity of secondary light-charged particles emitted by the two primary excited fragments in the exit channel. No evidence is observed for ternary-breakup processes, as expected from the systematics recently established for incident energies below 15 MeV/nucleon and for a large number of reactions. The binary-process results are compared with predictions of statistical-model calculations. The calculations were performed using the Hauser-Feshbach method, based on the available phase space at the scission point of the compound nucleus. This new method uses temperature-dependent level densities and its predictions are in good agreement with the presented experimental data, thus consistent with the fusion-fission origin of the binary fully-damped yields.

The search and study of quasi-molecular resonances in the 31 P composite system populated via two entrance channels are performed with two different experimental techniques. The 16 O + 15 N reaction products have been studied by the γ-ray detection method at cm. energies ranging from 15.5 MeV to 36.1 MeV. Binary channels of the 16 O + 15 N and 12 C + 19 F collisions have been studied by using the kinematical coincidence method at 26 incident energies ranging from E c.m. = 20.6MeV to 33.5MeV for the first system, and at energies corresponding to the same excitation energies of the composite system for the second system. The 16 O + 15 N reaction exhibits two prominent gross structures in the large angle elastic scattering excitation function correlated with the resonant structures observed in inelastic channel γ-ray yield measurements. Spin assignments were tentatively made for the two resonances. On the contrary, no such structures can be clearly established in the 12 C + 19 F system where only indications of non-correlated structures in various channels have been observed.

The experimental signature of the formation of a necklike structure, with a velocity between that of the projectilelike emitter and that of the targetlike emitter, is investigated with the same beam and experimental setup for targets lighter and heavier than the projectile. The reactions are ${}^{35}$Cl on ${}^{12}$C and on ${}^{197}$Au at 43 MeV/nucleon. Particle velocity distributions are compared with two-source statistical simulations and the presence of a necklike structure is inferred from the data. In the second part of the paper, dynamical model simulations with the formation of a necklike structure are presented for the ${}^{35}$Cl+${}^{12}$C system at 43 MeV/nucleon.

Binary-reaction channels of F-19+C-12 have been studied at E(lab)(F-19)=92 MeV using kinematic coincidence techniques. The results are discussed in the light of previous inclusive measurements performed at the same incidence energy and for which the occurrence of an important incomplete fusion mechanism after projectile breakup was proposed. Evidence for strong damped binary, especially quasisymmetric, decay processes is found.

The experimental signature of the formation of a necklike structure, with a velocity between that of the projectilelike emitter and that of the targetlike emitter, is investigated with the same beam and experimental setup for targets lighter and heavier than the projectile. The reactions are Cl-35 on C-12 and on Au-197 at 43 MeV/nucleon. Particle velocity distributions are compared with two-source statistical simulations and the presence of a necklike structure is inferred from the data. In the second part of the paper, dynamical model simulations with the formation of a necklike structure are presented for the Cl-35+C-12 system at 43 MeV/nucleon.

The breakup of the projectile 24Mg, excited in peripheral collisions on a gold target, has been investigated at 25 and 35A MeV with a large scintillation-detector array allowing exclusive measurements. Absolute breakup cross sections were deduced and the projectile-like nucleus velocity and excitation energy have been reconstructed. The excitation energy partition between the projectile and the target is found to lay between the limits of equal excitation energy sharing and equal temperature with some evolution from one limit to the other. The statistical nature of the decay mechanism is inferred from global variables. Small-relative-angle analysis is applied to the six-alpha exit channel and the corresponding data were found to be consistent with a sequential evaporation decay mechanism, with some contribution from sequential fission at higher excitation energies. The time scale involved in the breakup of 24Mg projectiles into the 6α and the 5αHH channels has been investigated by examining distortions in the fragment velocity distributions due to the Coulomb field of the target. A decrease in the quasi-projectile lifetime is observed as the mean excitation energy increases from 3.4 to 4.5A MeV.

A study of the reaction mechanisms in central 24Mg + 12C collisions at 25A and 35A MeV has been carried out. Global variables, such as anisotropy ratios and source-velocity ratios, computed for those events in which the total charge of the system has been detected, are compared to simulations based on statistical fragmentation codes. For violent events, a binary mechanism appears to be competing successfully with compound nucleus formation.

The properties of the two-body channels in the35Cl+24Mg reaction at a bombarding energy of 275 MeV, have been investigated by using fragment-fragment coincident techniques. The exclusive data show that the majority of events arises from a binary-decay process. The rather large number of secondary light charged-particles emitted from the two excited exit fragments are consistent with the expectations of the Extended Hauser-Feshbach Method. Therefore no evidence for the occurence of ternary break-up events is observed.

The fully energy-damped yields from the Cl+C reaction have been systematically investigated using particle-particle coincidence techniques at a Cl bombarding energy of ∼ 8 MeV/nucleon. The fragment-fragment correlation data show that the majority of events arises from a binary-decay process with rather large numbers of secondary light-charged particles emitted from the two excited exit fragments. No evidence is observed for ternary breakup events. The binary-process results of the present measurement, along with those of earlier, inclusive experimental data obtained at several lower bombarding energies are compared with predictions of two different kinds of statistical model calculations. These calculations are performed using the transition-state formalism and the Extended Hauser-Feshbach method and are based on the available phase space at the saddle point and scission point of the compound nucleus, respectively. The methods give comparable predictions and are both in good agreement with the experimental results thus confirming the fusion-fission origin of the fully-damped yields. The similarity of the predictions for the two models supports the claim that the scission point configuration is very close to that of the saddle point for the light V mass-asymmetry-dependent fission barriers needed in the transition-state calculation. PACS numbers: 25.70.Jj, 24.60.Dr, 25.70.Gh, 25.70.-z Typeset using REVTEX